1. Technical Field
The present invention relates to a light-emitting device having a light-emitting element which emits light according to the amount of current flowing from an anode to a cathode, such as an organic light-emitting diode element, and an image forming apparatus.
2. Related Art
In recent years, organic electroluminescent elements or organic light-emitting diode (OLED) elements, which are also referred to as light-emitting polymer elements, have been attracting much attention as next-generation light-emitting devices to replace liquid crystal devices. Image forming apparatuses having a line head, as an exposure unit, in which a plurality of OLED elements are provided for each line, have been developed. In the above-described line head, in addition to the OLED elements, a plurality of pixel circuits respectively having transistors for driving the OLED elements are arranged. For example, in Japanese Unexamined patent Application Publication No. 4-363264, a line head in which the OLED elements are provided in one line is disclosed.
However, the resolution of a printer depends on the pitch of the pixel circuits, and the luminance of the line head depends on the area of each OLED element. For this reason, it is important to optimally arrange elements constituting each pixel circuit. Further, impedance of power line is preferably low.